XJ6 & XJ12 Series I, II & III 1968-1992

The engine does not start - xj12

 
  #1  
Old 09-09-2016, 07:14 AM
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Default The engine does not start - xj12

I am currently restoring xj12.
After restoring the engine, the engine does not start.
I looked for the cause and found that only six injector injects fuel.
Like the photo I attached, only six injectors(red arrow) work and the other six(blue arrow) do not.
I want to know why.
I'm not a mechanic, but i am thinking the crank shaft position sensor or injecton power amplifier or the ecu as the cause.
I really need answers for this. I respectfully ask for help. Thank you.
 
Attached Thumbnails The engine does not start - xj12-20160909_152546.jpg   The engine does not start - xj12-20160514_113910.jpg   The engine does not start - xj12-20160226_143433_hdr.jpg  
  #2  
Old 09-10-2016, 04:15 AM
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Is this the XJ12C?????.

The V12 injectors are triggered in 4 groups of 3.

1,3,5A
2,4,6A
1,3,5B
2,4,6B.

Looking at your colour coded arrows, you have 2 banks of 3 working, and 2 banks of 3 NOT working.

I reckon you got a loom issue, or that amp is having a moment.

The engine snap is hard to pick which engine it is, the fuel rail is HE, but my PreHE had that rail also. The single coil indicates Pre Marelli, but some ID from yourself will get my slushy thinking a bit more clearer.

If its the PreHE with the trigger board for EFI activation, then that board or the wiring is also in question.
 
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  #3  
Old 09-10-2016, 09:41 PM
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Default Thank you

Yes, It's xj12c with Pre-HE engine.
Can you explain more about a loom issue?
Thank you for your help.




Originally Posted by Grant Francis View Post
Is this the XJ12C?????.

The V12 injectors are triggered in 4 groups of 3.

1,3,5A
2,4,6A
1,3,5B
2,4,6B.

Looking at your colour coded arrows, you have 2 banks of 3 working, and 2 banks of 3 NOT working.

I reckon you got a loom issue, or that amp is having a moment.

The engine snap is hard to pick which engine it is, the fuel rail is HE, but my PreHE had that rail also. The single coil indicates Pre Marelli, but some ID from yourself will get my slushy thinking a bit more clearer.

If its the PreHE with the trigger board for EFI activation, then that board or the wiring is also in question.
 
  #4  
Old 09-11-2016, 04:19 AM
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Its been a while, but here goes.

The amp on the radiator support panel does the firing of the injectors. The loom that travels from that amp to the engine and then down through the centre of the "V" is the item I am suspect of.

Somewhere near the oil cap, it a loom connector, I THINK, and this would a good place to start.

The loom itself, in its original position in all that heat etc, fails as time goes by. This usually has erratic injector issues, NOT the pattern you have.

These wiring drawings show the items I am talking of.

D Jetronic 1.pdf

D Jetronic 2.pdf

Let me know if you still need more, there are hundreds of pages of scribblings in the shed, from waaaaaay too many years with this system.

The trigger board connector near the oil switch is also on my radar. The switched inside that board trigger the banks of injectors, and if ONE is NOT working, I reckon the injectors you have AWOL are correct for that failure.
I would need to study the wiring diagram very carefully to establish which end of the trigger board operates which bank of injectors.
 

Last edited by Grant Francis; 09-11-2016 at 04:25 AM.
  #5  
Old 09-12-2016, 08:48 AM
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Default Your answer helps me a lot.

Thank you so much.
Your answer is so helpful.

I opened the amp, and there is no sign of defect. ( I attach a photo. 4 red arrows are the parts that affect 1A,3A,5A,2B,4B,6B which do not inject fuel.)

Only six injectors inject fuel.
and It seems all of 12 injectors spark.
In spite of that, Do you still reckon the trigger board?




Originally Posted by Grant Francis View Post
Its been a while, but here goes.

The amp on the radiator support panel does the firing of the injectors. The loom that travels from that amp to the engine and then down through the centre of the "V" is the item I am suspect of.

Somewhere near the oil cap, it a loom connector, I THINK, and this would a good place to start.

The loom itself, in its original position in all that heat etc, fails as time goes by. This usually has erratic injector issues, NOT the pattern you have.

These wiring drawings show the items I am talking of.

Attachment 135902

Attachment 135903

Let me know if you still need more, there are hundreds of pages of scribblings in the shed, from waaaaaay too many years with this system.

The trigger board connector near the oil switch is also on my radar. The switched inside that board trigger the banks of injectors, and if ONE is NOT working, I reckon the injectors you have AWOL are correct for that failure.
I would need to study the wiring diagram very carefully to establish which end of the trigger board operates which bank of injectors.
 
Attached Thumbnails The engine does not start - xj12-20160912_152414.jpg  
 
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